The isolated regime conducted its fifth and most powerful nuclear test on Friday just months after the U.N. imposed new economic penalties. Are sanctions good for anything?

A man walks past a television screen showing a news broadcast on North Korea's nuclear test at Gimhae International Airport in Busan, South Korea, on Friday, Sept. 9, 2016. North Korea conducted its fifth nuclear test on Friday, the anniversary of the reclusive nation's founding, and said it was now able to produce miniaturized nuclear arms. Photographer: SeongJoon Cho/Bloomberg via Getty Images

They were hailed as the most “comprehensive,” “robust” and “unyielding” sanctions to date against North Korea’s pariah government. Yet just six months after the U.N. Security Council voted unanimously to impose tougher penalties on Pyongyang for testing ballistic and nuclear weapons, the isolated regime has carried out its fifth and possibly most powerful nuclear test to date, creating a 5.3 magnitude tremor at the Punggye-ri test site.

In response to North Korea’s illicit blast, President Barack Obama vowed Friday to work with his Japanese and South Korean counterparts to impose “new sanctions” to show Pyongyang that there are “consequences to its unlawful and dangerous actions.” But because the previous round of sanctions failed to curb North Korea’s drive to advance its nuclear weapons program, doubts remain about the effectiveness of punitive economic measures on the world’s most isolated regime.

The device that was tested on Friday reportedly yielded 20 to 30 kilotons, a much more powerful blast than North Korea’s seven to nine kiloton detonation in January. Responding to that explosion, world diplomats agreed to a resolution in March calling for inspecting all cargo going to and from the country, a ban on all weapons trading with Pyongyang, and an expansion of specific Korean officials subject to sanctions. U.N. diplomats touted the measures as the most punishing to date, and a sign of closer cooperation between the United States and China, North Korea’s longtime patron.

But its failure to stop Pyongyang’s latest provocations is renewing skepticism that Washington’s favorite tool for penalizing Kim Jong Un’s regime will ever have any measurable impact.

“No amount of sanctions will stop North Korea,” Jae Ku, the director of the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies, told Foreign Policy. “Nuclear weapons are their sole survival strategy.”

Ku said as long as North Korea believes a nuclear arsenal is the only thing protecting it from Western efforts toward regime change, sanctions will have a limited impact.

Other critics agree that sanctions are largely useless, but for different reasons.

William Brown, a Korea expert at Georgetown University, said the regime has long understood how to maintain control of an isolated and blacklisted economy.

“Sanctions don’t have much impact on an economy that has been essentially bankrupt for a generation and which long ago lost its most important benefactors,” he said. “Sanctions may even help Kim control the flow of money to individuals that increasingly are seen as rivals to the state’s authoritarian controls, and even to Kim’s rule.”

But others are still holding out hope for sanctions to work — and say the reason the measures have yet to produce the desired effect has to do with time and enforcement.

“Expectations were that it would take about six months for sanctions impact to kick in — and that’s if China aggressively implemented them,” said Scott Snyder, a Korea expert at the Council on Foreign Relations.

Beijing was long thought to be a potential check on Pyongyang’s nuclear ambitions. But since Kim Jong Un took power, relations between the two capitals have soured. The North Korean dictator has never visited China as leader, nor has he met President Xi Jinping. Since taking power, Kim has purged many government officials with strong ties to China. This includes his uncle, Jang Song Thaek, whom he had executed.

Some experts accuse China of failing to enforce the March sanctions and point to the relative stability of North Korea’s economy as evidence.

Troy Stangarone, senior director for congressional affairs and trade at the Korea Economic Institute of America, said North Korea’s exports to China last spring dropped only 4 percent compared to the winter, and 14 percent from a year ago.

“This likely reflects a decline in the export price of coal rather than the effect of sanctions,” Stangarone said.

On Friday, Beijing and its state controlled media condemned the latest nuclear test, with China’s Xinhua news agency calling the detonation “unwise.”

“All parties, including North Korea, should recognize that tumult on the peninsular, war, and instability in Northeast Asia will benefit nobody,” the commentary said.

At the same time, China suggested that South Korea’s decision to move forward on its plans to host the Thermal High Altitude Area Defense (THAAD) system played a role in North Korea’s decision to conduct the test.

Stangarone dismissed Beijing’s claim, saying “the most significant driving factor” for Pyongyang was likely that it “reached a point where its technical research required a test to determine if a real breakthrough had been made in its weapons development process.”

He added that the reclusive regime appears to have made the “strategic decision that the cost of sanctions does not outweigh the strategic benefits of a verifiably workable nuclear weapon.”